An inclination sensor of this kind is described in "Zeitschrift fur Kulturtechnik und Flurbereinigung" 16, pages 296 to 303 (1975). In this inclination sensor the measuring cell includes a chamber filled with silicone oil in which the pendulum is movably suspended in the general region of the top of the chamber. On either side of the pendulum, which comprises an electrically conductive, ferromagnetic or permanently magnetic material, an inductive displacement sensor is arranged at an angle to the longitudinal axis of the inclination sensor which substantially corresponds to the maximum angular deflection of the pendulum. The measuring cell is suspended to be easily rotatable in the housing of the inclination sensor, since the pendulum and its point of suspension must always be in the vertical middle longitudinal plane of the measuring cell irrespective of the position of the sensor housing, so that it can rotate about its own axis while moving forward in a pipe line.
In this arrangement the pendulum always stays in its vertical position irrespective of the angular position assumed by the sensor. When the sensor is inclined relative to the pendulum the distance of the pendulum from one of the inductive displacement sensors is therefore reduced, while its distance from the other sensor is increased. This change in distance is a measure of the angular position of the sensor and can be displayed and/or recorded.
The demands on this sensor in respect of the sensitivity and accuracy with which the inductive sensors measure the deflection of the pendulum are very great, as the length of the pendulum can only be very small and the deflection of the pendulum relative to the inductive sensors is proportional to the angle and to the length of the pendulum. Thus with the known sensors, despite a relatively high outlay in apparatus, only relatively low accuracy of measurement can be achieved.